I am using DP:REST, DS:Mutable, and prepare_serializer_for_format(). I am querying for a JSON response via jQuery like so $.ajax({ url : .., type : "POST", data : "poly=" + JSON.stringify(coords_pix), dataType: "json", error : function() { alert("Error loading html document"); }, success : function(data) { .. do stuff with data .. } }); This is what I seen in Firebug Request Headers =============== .. Accept application/json, text/javascript, */*; q=0.01 .. Content-Type application/x-www-form-urlencoded; charset=UTF-8 X-Requested-With XMLHttpRequest Response Headers ================ Date Mon, 27 Dec 2010 13:23:35 GMT Server Apache/2.2.16 (Unix) DAV/2 mod_perl/2.0.4 Perl/v5.12.1 X-Powered-By Perl Dancer 1.2003 Content-Type text/xml; charset=UTF-8 .. Gak! what happened there? Why did I get back xml even though I requested json? (Note: It is possible that I don't understand accept and response headers at all, in which case, kindly educate me). As a result, Firebug show the JSON output correctly, but complains about the XML output XML Parsing Error: not well-formed Location: moz-nullprincipal:{5063a87c-f476-8346-8452-ab404f4c1282} Line Number 1, Column 1: {"harvest_amt":"14188.62","harvest_area":"126100.00","nep":"404789.50"} ^ -- Puneet Kishor http://punkish.org Carbon Model http://carbonmodel.org Charter Member, Open Source Geospatial Foundation http://www.osgeo.org Science Fellow http://creativecommons.org/about/people/fellows#puneetkishor Nelson Institute, UW-Madison http://www.nelson.wisc.edu --------------------------------------------------------------------------- Assertions are politics; backing up assertions with evidence is science ===========================================================================